MetroTwit is a slick Twitter client for Windows.

Infinite scrolling - If you ever want to read more tweets, just scroll down and more will appear almost instantly.
URL shortening and previews - Take control of links with an intuitive URL shortener that automatically saves you space and time tweeting.
Autocomplete for usernames & hashtags - The people and topics you care about, at your fingertips. Simply start typing any part of a username or hashtag and we'll find them for you.
Resizable and reorderable columns - Not all columns must be created equal. You have the choice and flexibility to control exactly how your columns should look.